OK, all done. 45 minutes total on the phone. Agent REALLY knew her stuff, very impressed. Our old/current e-ticket now shows just the UA segment exchanged/reissued; rest are (past) flown or (future) open for use/airport control; and we have a special new e-ticket that covers just the one SQ segment.

Checked in online with SQ and now have boarding passes HKG-SIN. Verified PNR with SQ etc. Will probably need do some work with our downline TG/LH flights on Saturday to make sure we check in with the correct e-ticket. May have some trouble making changes to the return portion of this award trip; phone agent advised us NOT to change anything until after we arrive in Singapore because we don't want to fly any coupons out of order or anything.

Yes, we've been lucky to see very little irrops this year except for the oversale on a LHR flight (where we noticed an oversale due to equipment swap, then (1) called the special oversale line and said "hi, um, our flight is dramatically oversold, do you want to rebook us?" and they said "no, go away", then (2) got a email telling us to call the special oversale line and called and they offered us a much better deal than we would have taken); and for this mx.